The incidence of Bacillus cereus spores ihn algerian raw milk: a study of the chief sources of contamination

摘要

This paper presents a study of the sources of contamination and the incidence of Bacillus cereus spores in raw milk from twelve farms scattered over the West of Algeria, covering a period of two years, A total of 46 out of the 192 samples of first milk taken from individual cows were found to be positive (≥ 10 cf u/ml). Counts higher than 10~4 cfu/ml were noted in five samples B. cereus was detected in 50 (26,32%) out of 190 samples of milk taken from milking machines. In two of these 50 positive samples (4%), the counts of B. cereus exceeded 10~5 cfu/ml. In raw milk taken from bulk tanks at the dairy processing plant, this spore-forming microorganism was present in 21 out of 148 samples, yielding viable counts in the range 10 to 10~5 cfu/ml, In order to determine the chief sources for contamination of raw milk on farms, samples were taken from the air (n=190), used bedding (n=192), udders (n=189), and the inner surfaces of milking machines (n=130) and milk collection tanks (n=151), B. cereus wasisolated from all the environmental sources examined, although the incidence varied from 26.49% (udders) to 53.08% (milking machines). The levels present ranged from <10 to 10~5 cfu/g or 25 cm~2. The major contamination sources for 6. cereus spores werethe milking machines and milk collection tanks. Small numbers (10-10~2 cfu/plate) were present in the air.